I would love to have that information myself. Anyone can recommend a good book about orbital dynamics? (does that cover launching as well? rocket equation and all?).

Dan Frederikson asked a question the other day in the Armadillo forum (to be honest, that has been the only time so far I've seen him ask an interesting question instead of insulting people...) and I really wanted to answer that question. Unfortunately I couldn't find the formulas to do the math

I tried wikipedia but their information doesn't go into details about the physics, and math behind such a system.

The reason i am asking is because a couple of years ago i was wondering about the smallest rocket buildable at current technology that could put something like 1 g into orbit.

Purely because i was dreaming about building one. I hoped it would fit within my budget.

But i lost interest for some reason, probably got distracted by other stuff. I get very easily distracted by other interests...

Then when i got here and saw the n-prize my interest peaked again.

Especially if i could pair this interest with my other current interest which is a crowd funded crowd sourced space program.

It seems like this might be a suffiently small budget project a smaller crowd of a couple of thousand people could possibly tackle quite fast.

So i could use this for starting to grow the crowd. First i thought we could focus on lunar x prize, but that project needs way more capital, which means way larger crowd before we could do something serious.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Team Prometheus developed a plan for doing a rockoon launch about 2.5 years ago. After Monroe decided to use a different approach he gave me permission to post the orignal plan, which is located at https://sites.google.com/site/davehein3 ... ects=0&d=1 . This might provide some useful background on how a rockoon approach would work.

One of the issues that was still open at the time was how to stabalize the rocket. The document proposes using spin stabalization. However, I now believer that approach is inadequate, and active stablization is required.

Has a few links but most easily available stuff refers to the late 40's and early 50s experiments and like air flight moved from air ships to heavier than air planes the technology seems to have been left behind as one set of technologies got more investment and was supported over the other a bit like betamax and vhs

It is my belief that with modern materials technologies new types of Rockoon could supplant traditional rocketry systems but its going to take a lot of calculations and testing to prove it.

Launching at height reduces both gravitational losses and air resistance considerably also rockets can be designed to work optimally in atmosphere or in vacuum and is usually a bit of a compromise tho staging helps in this but if you want to use less stages the higher you are the less of a compromise you can have.

But as Dave H says stability is an issue and not a trivial one tho i think the above advantages will out weigh it.

Your right the prize is a way to draw out the more lateral thinking type ideas and see if they can be made to work.

And although curiosity may have killed the cat it has given humanity its civilisation.

_________________Someone has to tilt at windmills.So that we know what to do when the real giants come!!!!

Team Prometheus developed a plan for doing a rockoon launch about 2.5 years ago. After Monroe decided to use a different approach he gave me permission to post the orignal plan, which is located at https://sites.google.com/site/davehein3 ... ects=0&d=1 . This might provide some useful background on how a rockoon approach would work.

One of the issues that was still open at the time was how to stabalize the rocket. The document proposes using spin stabalization. However, I now believer that approach is inadequate, and active stablization is required.

Thank you for that, that pretty much answered my questions.

What do you mean by active stabilisation? Movable fins, movable nossle, or an internal gyroscope?

Active stabilization could use fins on the first stage, and maybe on the second stage. It would require movable nozzles or thrust deflectors on the upper stages. The final stage might even have a gimbal mount between the rocket motor and the payload section, so that it basically bends in the middle.

A gyro would be needed to determine orientation. It could be calibrated using a sun-position detector (i.e., an imaging device) and a horizon detector. An accelerometer would also be needed to determine velocity and altitude.

Some small firework is probably the smallest, unless there are some geeks out there actively trying to make tiny rocket motors. Yes, by far most model rockets use solid rocket motors that are bought pre-made. Experienced builders making more powerful rockets may cast their own solids, or even go for hybrids or liquid fuel engines. The thing with liquids is that you need plumbing, some kind of pressurisation, valves, something to remotely control the valves, and so on. A solid rocket engine is just a tube with a curiously shaped slug of explosives in it and a nozzle. It's much easier to make. (Not easy of course, and melting down and casting something that goes boom easily enough to be useful as a rocket propellant is still dangerous, but easier.)

[Edit: just noticed that the question is about the smallest liquid fuel rocket specifically. I have no idea about that.

_________________Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhereWhat is this spell we’re under, do you care? The might to rise above it is now within your sphereMachinae Supremacy – Sid Icarus

Last edited by Lourens on Sat Jun 02, 2012 6:46 pm, edited 1 time in total.

The videos are very interesting. Have you been able to determine the impulse and ISP of your motors? I wonder about using Coke cans for the motor casing. Assuming that you can resolve the burn-through issues, won't these burst at a pressure around 100 PSI? That pressure is much too low for an efficient motor. Have you considered reinforcing the Coke can motor casing with carbon fiber, or some other material with a higher tensile strength?

Some small firework is probably the smallest, unless there are some geeks out there actively trying to make tiny rocket motors. Yes, by far most model rockets use solid rocket motors that are bought pre-made. Experienced builders making more powerful rockets may cast their own solids, or even go for hybrids or liquid fuel engines. The thing with liquids is that you need plumbing, some kind of pressurisation, valves, something to remotely control the valves, and so on. A solid rocket engine is just a tube with a curiously shaped slug of explosives in it and a nozzle. It's much easier to make. (Not easy of course, and melting down and casting something that goes boom easily enough to be useful as a rocket propellant is still dangerous, but easier.)

[Edit: just noticed that the question is about the smallest liquid fuel rocket specifically. I have no idea about that.

Thanks for the answer anyway.

I am just wondering about the physics behind it, how rockets using liquid and solid propellants compare as you decrease the size and mass of the rocket.

Back when I was a kid I wanted to make a rocket out of the small lighter refiller cans. I should have actually tried, it would have been a lot of fun. Well as long as everything was done "safely".

Solid fuel rockets are simple in design and don't have much in the way of additional weight penalty's.

But a liquid rocket needs lots of complex plumbing, pumping, heating and cooling extras which will reduce the overall ISP because of this additional weight penalty.

All the complex stuff tends to benefit from the inverse square law so the bigger it is the proportional weigh penalty of gear against fuel lowers allowing you to take advantage of the liquid fuels better ISP.

This is a complex set of variables and the best size will constantly change as materials and other technologies improve.

_________________Someone has to tilt at windmills.So that we know what to do when the real giants come!!!!